The Galápagos Islands are known for their unique and diverse wildlife, and the marine iguanas (Amblyrhynchus cristatus) is no exception. These fascinating reptiles are one of the few species of iguana that have adapted to life in the ocean, and they are truly a sight to behold. With their distinctive appearance and behavior, marine iguanas are a photographer’s dream, offering endless opportunities to capture their beauty and grace.

Not only are marine iguanas fascinating to observe, but they are also a crucial part of the Galápagos ecosystem. These reptiles feed on seaweed and other marine plants, playing an important role in maintaining the balance of the island’s marine communities. They are also able to tolerate high levels of salt in their bodies, which allows them to dive deeper into the ocean in search of food.

I have always been passionate with marine iguanas and their ability to dive below water to feed on algae. During a trip to Galápagos Islands I had the opportunity to observe them in nature and photograph their behavior. In this post I made small collection of images from these incredible animals using a Nikon D90 with a Sigma 10-20mm lens, Nikkor 100-200 lens and an Ikelite housing for the underwater images.

Basking in the Sun: Marine iguanas are the only lizards that forage in the sea, bask in the sun on dark volcanic rocks to maintain their body temperature and conserve energy in the harsh environment of the Galápagos

Marine iguanas are the only species of lizard that forage in the sea, making them a unique and fascinating species to study. Found exclusively in the Galápagos Islands, these cold-blooded reptiles are unable to regulate their body temperature like most reptiles can. Instead, they rely on external heat sources to maintain their body temperature, a process known as ectothermy.

To do this, marine iguanas bask in the sun on the dark volcanic rocks that are found on the Galapagos Islands. These rocks are able to absorb heat quickly and retain it for long periods of time, making them the perfect place for the iguanas to rest and warm up. In addition, by laying on the rocks in groups, the iguanas are able to conserve their energy and reduce their risk of predation.

This adaptation to ectothermy has allowed the marine iguanas to thrive in the harsh environment of the Galápagos. However, there are also challenges to this approach. If the iguanas are unable to bask in the sun for long periods of time, they may become sluggish and unable to forage for food effectively. This is because their metabolic rate is directly related to their body temperature. When their body temperature drops, so does their metabolic rate, meaning they need to warm up in order to function properly.

Foraging in the Sea: Marine iguanas in the Galápagos Islands have adapted to foraging in the sea for their primary source of food – macroalgae, including red algae such as Centroceras, Gelidium, and Polysiphonia

Marine iguanas have a unique feeding behavior that sets them apart from other lizards. They are the only species of lizard that forage in the sea, and their primary source of food is macroalgae. Large males are known to dive to find macroalgae, while smaller males and females feed during low tide in the intertidal zone. This is because large males have the ability to dive deeper and for longer periods of time, allowing them to access a wider range of macroalgae species.

At least 10 genera of algae are regularly consumed by marine iguanas in the Galápagos, including the red algae Centroceras, Gelidium, Grateloupia, Hypnea, Polysiphonia, and Pterocladiella. These macroalgae are a rich source of nutrients, including protein, fiber, and minerals such as calcium and iron.

The feeding habits of marine iguanas are directly tied to their ability to thermoregulate, as they rely on external heat sources to maintain their body temperature. Because they spend a significant amount of time in the water, they need to consume a large amount of macroalgae in order to maintain their energy levels and body temperature.

Despite the challenges associated with foraging in the sea, marine iguanas have adapted to this unique feeding behavior and thrive in the Galápagos Islands. Their ability to access a wide range of macroalgae species and their ability to conserve energy through communal thermoregulation has allowed them to become a successful and fascinating species.

Diving and Feeding Habits: Marine iguanas in the Galápagos Islands are expert divers, with the ability to dive as deep as 30 meters and spend up to an hour underwater while foraging for food

Marine iguanas have evolved to become expert divers, with the ability to dive as deep as 30 meters and spend up to an hour underwater. This is a remarkable feat for a reptile, and is made possible by their unique adaptations, including a flattened tail that acts like a rudder, and a high concentration of red blood cells that allows them to store more oxygen.

While foraging, marine iguanas tend to return to specific feeding sites day after day, with most individuals feeding daily. However, large offshore males may only feed every second or third day, as they require a larger amount of food to maintain their energy levels and body temperature. During bad weather with high waves, marine iguanas are unable to feed, sometimes for more than a week. This is because the high waves make it difficult for the iguanas to find and access their food sources, and can also make it dangerous for them to enter the water.

Interestingly, large males often do not feed for several weeks when maintaining a breeding territory. This is because they need to conserve their energy for fighting off rivals and mating with females.

Remarkable Diving Capabilities: Marine iguanas in the Galápagos Islands have a unique ability to dive and forage in the ocean, thanks to adaptations such as their flattened tail that acts as both a propeller and a rudder.

When diving, marine iguanas use their powerful front legs to paddle through the water, while their flattened tail helps to propel them forward and steer them in the right direction. The tail is also used to stabilize the iguana’s body while swimming, making it easier for them to navigate through the ocean currents. Another adaptation that allows marine iguanas to dive and forage in the ocean is the high concentration of red blood cells in their bloodstream. This allows them to store more oxygen and stay underwater for longer periods of time, making it possible for them to find food sources that other reptiles cannot access.

Despite these adaptations, diving and foraging in the ocean is still a dangerous and challenging activity for marine iguanas. They are vulnerable to predators such as sharks and sea lions, and can also be affected by changes in ocean temperature and weather conditions.

Sleeping Habits: A group of marine iguanas sleeping on a rocky outcropping in the Galápagos Islands, conserving energy and avoiding predators while waiting for the sun to warm their bodies

Marine iguanas spend a large portion of their time sleeping or resting. This behavior is not unique to marine iguanas, but is especially pronounced in this species due to their unique physiology and ecology. One reason why marine iguanas spend so much time sleeping is due to their need to conserve energy. These cold-blooded reptiles rely on the heat of the sun to regulate their body temperature and metabolism, and when temperatures are low or food is scarce, they may become sluggish and inactive. Sleeping allows them to conserve energy and avoid unnecessary movement, helping them to survive in the challenging conditions of the Galápagos Islands.

Additionally, marine iguanas may also sleep to avoid predators. While they are not at the top of the food chain, they are well-camouflaged and have few natural enemies. By remaining still and hidden, they can avoid detection and reduce their risk of being attacked. Despite their seemingly lazy lifestyle, marine iguanas are capable of moving quickly and are adept swimmers and divers. They have evolved to thrive in the challenging conditions of the Galápagos Islands, and their unique behavior is just one of the many adaptations that have allowed them to survive and thrive in this unique ecosystem.

The Moulting Process: A marine iguana in the Galápagos undergoing the moulting process, shedding its old skin to grow a new waterproof layer that helps protect it from parasites and other threats.

Marine iguanas undergo a process of moulting their skin, much like snakes and other reptiles. During the moulting process, which occurs once or twice a year, the marine iguana sheds its old skin and grows a new one, which allows them to maintain their waterproof skin and helps protect them against parasites and other threats.

The moulting process can take several days or even weeks, during which time the iguana will often retreat to a secluded spot to rest and recover. The process is often accompanied by a noticeable change in the iguana’s behavior, as they may become more sluggish and inactive while they shed their skin.

For scientists and photographers, the moulting process is an interesting phenomenon to observe, as it provides a rare opportunity to witness the iguanas shedding their skin up close. However, it’s important to remember that during this time the iguanas may be more vulnerable and should be approached with caution.